Potassium sodium niobate ceramics with single crystal

Abstract

Disclosed is a (K,Na)NbO 3 (abbreviated by “KNN”)-based single crystal ceramic. The KNN-based single crystal ceramic according to the present disclosure is formulated by (K 0.5−x/2 Na 0.5−x/2−y □ y/2 M x+y/2 )Nb 1−x/3+y O 3 , wherein M indicates a metal having a different valence from Na, and □ indicates a metal vacancy. The above formulated KNN-based single crystal ceramic allows compensating for the volatilization of Na in a growing grain due to the addition of M 2+ ions, and substituting M 2+ ions for Na + ions to form metal vacancies, thereby making possible the single crystal growth.

What is claimed is: 
     
       1. A KNN-based single crystal ceramic represented by the following formula:
   (K 0.5−x/2 Na 0.5−x/2−y □ y/2 M x+y/2 )Nb 1−x/3+y O 3 ,
 
 wherein M indicates a metal having a different valence from Na, □ indicates a metal vacancy, 0.01≤x≤0.02, and 0.0≤y≤0.5, and 
 wherein the KNN-based single crystal ceramic has a grain size of 0.1 cm or more. 
 
     
     
       2. The KNN-based single crystal ceramic of  claim 1 , wherein the element M is a divalent element. 
     
     
       3. The KNN-based single crystal ceramic of  claim 1 , wherein the element M comprises at least one of Ba, Sr or Ca. 
     
     
       4. The KNN-based single crystal ceramic of  claim 1 , wherein at least one of K, Na, and Nb is substituted with other element, and the metal vacancy is formed due to the element M. 
     
     
       5. The KNN-based single crystal ceramic of  claim 1 , wherein the KNN-based single crystal ceramic is produced by:
 preparing a raw material mixture comprising a K-containing compound, a Na-containing compound, an M-containing compound, and an Nb-containing compound; 
 subjecting the raw material mixture to a calcination to form a calcined product; 
 milling the calcined product to form a milled product, wherein milling the calcined product comprises adding a Cu-containing compound to the calcined product; and 
 sintering the milled product. 
 
     
     
       6. The KNN-based single crystal ceramic of  claim 1 , wherein a single crystal portion of the KNN-based single crystal ceramic has a piezoelectric voltage coefficient (g 33 ) of 100 [10 −3  Vm/N] or more.